You may not know much about valley fever. Science knows little about it.

What is clear is that construction of the peripheral tunnel calls for a whole lot of digging. In many parts of the Valley, digging releases coccidioides, a fungus that lives in the arid soil of the American southwest (and semi-arid Valley soil).

The fungus causes valley fever.

Sixty percent of people who inhale the spores do not get sick. About 39 percent develop "flu-like symptoms that may last for weeks to months," according to the Center for Disease Control and Prevention.

Imagine flu-like symptoms for months.

About 9 percent of this group develop pneumonia.

Worse, "In a very small proportion of people who get valley fever, the infection can spread from the lungs to the rest of the body and cause more severe conditions, such as meningitis or even death," the CDCP reports.

For this 1 percent, valley fever is a pathogenic pantry of many diseases that can blind, strangle, rob energy, wreck the mind or leave the infected in lifelong pain.

"It destroys lives," a doctor told the New York Times last week. "Divorces, lost jobs and bankruptcy are incredibly common, not to mention psychological dislocation."

The CDCP calls valley fever a "silent epidemic."

As we know all too well, Gov. Jerry Brown is pushing a twin-tunnel project to secure Delta water for much of the state: two trans-Delta tunnels, 40 feet in diameter, 150 feet deep, spanning 35 miles.

The biggest dig of our times.

Excavating an underground Panama Canal will exhume 22 million cubic yards of earth ("tunnel muck") over perhaps 7.5 years, according to the Bay-Delta Conservation Plan's Environmental Impact Report.

So it would seem that if valley fever is out there, this project will dig it up. The question is how endemic it is to the soil. Not at all? An inconsequential sprinkling? More?

Nobody knows.

"No studies have been done," said Karen Furst, San Joaquin County's public health officer.

The problem is the "cocci" organism cannot be easily cultured from soil. "You cannot easily do studies for where it is. I can only say where the valley fever cases occur."

Valley fever is so intense farther down the Valley that the courts recently ordered the state to move 2,600 vulnerable prisoners out of two Bakersfield-area prisons.

It appears that the spore's range extends northward up the Valley at least mildly into the semi-arid soil of southwest San Joaquin County. The highest incidences of it in this county are in the city of Tracy - though hundreds of cases across the county have been reported over the past decade.

Meaning hundreds more undiagnosed or misdiagnosed cases occurred but went unreported.

And "The rate of reported cases of coccidioidomycosis in San Joaquin County generally increased over the last decade," according to a county Public Health Services 2011 report.

Perhaps the Delta is the boundary of the valley fever range. Perhaps "cocci" don't like Delta soils.

If they do, they live near the surface, and, "The tunneling that would occur happens deep underground, and doesn't impact that surface, ..." said Richard Stapler, a spokesman for the state Natural Resources Agency

Stapler added, "Surface disturbances would occur in areas that are possibly a few hundred acres, and potentially less."

Lauren Bisnett, a spokeswoman for the California Department of Water Resources, commenting for an earlier blog post I did on this subject, said builders will take care to minimize dust.

"While valley fever is not considered a project-specific problem, it is something we're aware of and would respond to accordingly should it be detected," Bisnett said.

It's not considered a "project-specific problem" in part because there's a void of information. There's no basis to expect a plague of valley fever spores to rain on San Joaquin County. But it would be nice to know for sure.

Furst: "These are good questions as to what kind of issues we need to be concerned about as this canal gets built."